Prognostic significance of BRAF and NRAS mutations in melanoma: a German study from routine care

Abstract

Background: Hotspot mutations of the oncogenes BRAF and NRAS are the most common genetic alterations in cutaneous melanoma. Specific inhibitors of BRAF and MEK have shown significant survival benefits in large phase III trials. However, the prognostic significance of BRAF and NRAS mutations outside of clinical trials remains unclear.

Methods: The mutational status of BRAF (exon 15) and NRAS (exon 2 and 3) was determined in melanoma samples of 217 patients with pyrosequencing and Sanger sequencing. The genotypes were correlated with clinical outcomes and pathologic features of the primary tumors. Time to disease progression was calculated with the cumulative incidence function. Survival analyses were performed with Kaplan-Meier estimates and Cox proportional hazards regression analysis. Relative survival was calculated with the Ederer-II method. Treatment with BRAF and MEK inhibitors and immune checkpoint blockade (ICB) was allowed.

Results: Mutations in BRAF and NRAS were identified in 40.1 and 24.4% of cases, respectively. Concurrent mutations in both genes were detected in further 2.3%. The remaining 33.2% were wild type for the investigated exons (WT). BRAF mutations were significantly associated with younger age at first diagnosis (p < 0.001) and truncal localization of the culprit primary (p = 0.002). The nodular subtype was most common in the NRAS cohort. In addition, NRAS-mutant melanoma patients showed a higher frequency of nodal relapse (p = 0.013) and development of metastatic disease (p = 0.021). The time to loco-regional nodal relapse was shortest in NRAS-mutant melanoma (p = 0.002). Presence of NRAS mutation was an independent risk factor for disease progression in multivariate analysis (HR 2.01; 95% CI 1.02 - 3.98). BRAF-mutant melanoma patients showed a tendency for better overall and relative survival. Genotype was not a consistent risk factor in multivariate analysis. Instead, positive sentinel lymph node status (HR 2.65; 95% CI 1.15 - 6.10) and treatment with ICB in stage IV disease (HR 0.17; 95% CI 0.06-0.48) were significant multivariate risk factors.

Conclusions: NRAS-mutant tumors tended to behave more aggressively particularly in early stages of the disease in this high-risk melanoma population. Treatment with immune checkpoint blockade improved survival in stage IV disease in a real-world setting.

Keywords: BRAF; BRAF inhibitor; Disease progression; Immune checkpoint blockade; MEK inhibitor; Melanoma; NRAS; Nodal relapse; Overall survival; Survival analysis.

Fig. 1

Time from primary diagnosis to first disease progression of any type (a), first loco-regional relapse (b), and first detection of distant metastases (c). Times to the respective events were calculated with the cumulative incidence function and are indicated in years. The BRAF mutant cohort showed the longest time to progression with the median time to first nodal relapse not being reached in the observation period (b). In contrast, the NRAS mutant cohort had the shortest time to nodal relapse (b), while the median time to progression of any type (a) or to the formation of distant metastases (c) was almost equal in NRAS mutant and WT melanoma patients. Patients who initially presented with stage IV disease (n = 8) were precluded from the analyses shown in (b) and (c). The right panels of (b) and (c) indicate progression curves after selection for patients with relapse. The indicated p-values were calculated with the Gray’s test

Fig. 2

Post-progression survival after first disease progression of any type (a), first nodal relapse (b), and metastatic disease (c). All three genotypes showed similar Kaplan-Meier curves for survival after any disease progression (a) and loco-regional nodal recurrence (b). Patients who were mutant for NRAS showed a slightly shorter median survival in stage IV disease (1.8 years) compared to patients with BRAF mutant (2.2 years) and WT (2.5 years) melanoma. However, this difference was not significant. The indicated p-values were calculated with the log-rank test

Fig. 3

OS and relative survival from diagnosis of the culprit melanoma. a + c Kaplan-Meier curves are shown for overall survival according to genotype for the entire cohort (a) and after selection for patients with relapse (c). BRAF-mutant melanoma patients showed a trend towards longer survival compared to NRAS-mutant and WT melanoma patients, which was significant in patients with relapse only. The indicated p-value was calculated with the log-rank test. b + d Relative survival was defined as ratio of the observed survival of the study cohort to the expected survival of a reference population to adjust for cause- and age-specific mortality. Similar results were observed compared to the Kaplan-Meier curves from (a) and (c)